#include "figure-17.17.h"
#include <sys/uio.h>        /* struct iovec */

/*
 * Open the file by sending the "name" and "oflag" to the
 * connection server and reading a file descriptor back.
 */
/* figure-17.2.c figure-17.14.c figure-17.17.c */
int
csopen(char *name, int oflag)
{
    pid_t           pid;
    int             len;
    char            buf[10];
    struct iovec    iov[3];
    static int      fd[2] = {-1, -1};

    /* 这里利用fork操作，在子进程中与opend通信(UNIX域套接字(匿名)) */
    if (fd[0] < 0) {    /* fork/execl our open server first time */
        if (fd_pipe(fd) < 0) {  /* figure-17.2.c */
            err_ret("fd_pipe error");
            return(-1);
        }
        if ((pid = fork()) < 0) {
            err_ret("fork error");
            return (-1);
        } else if (pid == 0) {      /* child */
            close(fd[0]);
            if (fd[1] != STDIN_FILENO &&
                dup2(fd[1], STDIN_FILENO) != STDIN_FILENO)
                err_sys("dup2 error to stdin");
            if (fd[1] != STDOUT_FILENO &&
                dup2(fd[1], STDOUT_FILENO) != STDOUT_FILENO)
                err_sys("dup2 error to stdout");
            if (execl("./opend", "opend", (char *)0) < 0)
                err_sys("execl error");
        }
        close(fd[1]);
    }
    sprintf(buf, " %d", oflag);             /* oflag to ascii */
    iov[0].iov_base = CL_OPEN " ";          /* string concatenation */
    iov[0].iov_len  = strlen(CL_OPEN) + 1;
    iov[1].iov_base = name;
    iov[1].iov_len  = strlen(name);
    iov[2].iov_base = buf;
    iov[2].iov_len  = strlen(buf) + 1;      /* +1 for null at end of buf */
    len = iov[0].iov_len + iov[1].iov_len + iov[2].iov_len;
    if (writev(fd[0], &iov[0], 3) != len) {
        err_ret("writev error");
        return(-1);
    }

    /* read descriptor, returned errors handled by write() */
    return(recv_fd(fd[0], write));  /* figure-17.14.c (没有必要使用figure-17.16.c)*/
}
